Capacitors having a large capacitance per unit volume can be made by utilizing an electrochemical double layer. Such electrochemical double-layer capacitors comprise a plurality of porous electrodes having a large internal surface area, the electrodes being in contact with an electrolyte having high conductivity. In multi-cell designs in order to realize nominal voltages higher than the decomposition voltage of the electrolyte, the individual electrolyte chambers must be separated from each other.
The large internal surface area required for such electrodes can be achieved, for instance, by using bound activated carbon (DE-OS 30 00 777 or U.S. Pat. No. 4,327,400 and DE-OS 30 46 252 or U.S. Pat. No. 4,394,713) or activated vitreous carbon (DE-OS 30 11 701 or "Chemical Abstracts", vol. 95 (1981) no. 22 (page 640), 196226g). In this connection, activated vitreous carbon provides good electrical and mechanical properties, it is easily shaped and provides the required gas-tightness. However, only relatively thin layers of activated vitreous carbon with a thickness of about 10 to 50 .mu.m can be produced by conventional methods and consequently they only produce a capacitance of some 100 mF.multidot.cm.sup.-2. On the other hand, a double layer capacitance of up to 10 F.multidot.cm.sup.-2 can be achieved with bound activated carbon due to its high porosity (with electrodes about 1 mm thick). However, these electrodes must be supported mechanically and individually sealed. Furthermore, only moderate electronic conductivities may be realized in these capacitors because of the binders used.